One or more embodiments of the subject matter herein relate to quantifying and localizing left ventricular (LV) electrical conduction non-uniformity based on sensed events along a multipolar LV lead.
Implantable stimulation devices or cardiac pacemakers are a class of cardiac rhythm management devices that provide electrical stimulation in the form of pacing pulses to selected chambers of the heart. As the term is used herein, a pacemaker is any cardiac rhythm management device with a pacing functionality regardless of any additional functions it may perform, such as cardioversion/defibrillation.
A pacemaker is comprised of two major components, a pulse generator and a lead. The pulse generator generates the pacing stimulation pulses and includes the electronic circuitry and the power cell or battery. The lead, or leads, is implanted within the heart and has electrodes which electrically couple the pacemaker to the desired heart chamber(s). A lead may provide both unipolar and bipolar pacing and/or sensing configurations. In the unipolar configuration, the pacing pulses are applied (or responses are sensed) between an electrode carried by the lead and a case of the pulse generator or a coil electrode of another lead within the heart. In the bipolar configuration, the pacing pulses are applied (or responses are sensed) between a pair of electrodes carried by the same lead. Pacemakers are also described as single-chamber or dual-chamber systems. A single-chamber system stimulates and senses in one chamber of the heart (an atrium or a ventricle). A dual-chamber system stimulates and/or senses in at least one atrial chamber and at least one ventricular chamber. Recently, pacing systems have been introduced that stimulate multiple sites in the same chamber, termed multisite stimulation systems or multi-purpose pacing systems.
When the patient's own intrinsic rhythm fails, pacemakers can deliver pacing pulses to a heart chamber to induce a depolarization of that chamber, which is followed by a mechanical contraction of that chamber. Pacemakers further include sensing circuits that sense cardiac activity for the detection of intrinsic cardiac events such as intrinsic atrial depolarizations (detectable as P waves) and intrinsic ventricular depolarizations (detectable as R waves). By monitoring cardiac activity, the pacemaker circuits are able to determine the intrinsic rhythm of the heart and provide stimulation pacing pulses that force atrial and/or ventricular depolarizations at appropriate times in the cardiac cycle when required to help stabilize the electrical rhythm of the heart. This therapy is referred to as cardiac resynchronization therapy (CRT).
Recently, multi-point pacing (MPP) technology has enabled pacing at left ventricular (LV) sites to improve synchrony in cardiac resynchronization therapy (CRT) patients. Improvements in synchrony and improved hemodynamic response have been shown to depend on the MPP configuration. In the past, MPP configurations have been selected based on reducing pacing capture thresholds, avoiding atrial and phrenic nerve capture, and maximizing anatomical distance between two LV pacing sites. However, addressing the non-uniformity of electrical conduction at the four LV electrodes, due to local dyssynchrony in the surrounding heart tissue, may enhance the benefit of MPP. A need remains for improved methods and systems to identify preferred MPP configurations.